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Immunochemical techniques in biological monitoring.

Biological monitoring is the assessment of exposure to an agent through the measurement of biomarker(s) that result from contact with the agent(s). Examples are zinc protoporphyrin in blood, levels of which increase with lead exposure because lead inhibits the biosynthesis of heme; protein and DNA adducts of aromatic amines in blood that can both reflect the intensity of exposure and be correlated with the biologically effective dose; antibodies (Abs) produced against low-molecular-weight molecules-some chemicals, although not immunogenic in their own right because of small size and other limitations, may bind to constitutive polymers (such as host proteins) and become immunogenic, causing the production of specific antibody (Ab). Alternatively, such exposures may lead to the production of new antigenic determinants through non-adduct-forming reactions between the agent and selected protein-carrier molecules. Abs can be made to these modified proteins or to the parent hapten-conjugate. In both cases, the Abs may remain in the human system much longer than the toxicant that initiated their development. Biomarkers have been trichotomized into biomarkers of exposure, effect, and susceptibility [1]. Biomarkers of exposure are defined as biomarkers that quantify the body burden of chemicals or metabolites of the initial xenobiotic. Biomarkers of effect detect functional change in the biological system under study. Biomarkers of susceptibility indicate the inter-individual variation bas d on host-susceptibility or genetic differences that can increase or decrease susceptibility. In some cases, a biomarker may simultaneously be a biomarker of exposure, effect, and susceptibility (such as specific IgE in allergies) [2].